<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div class="container">
    <h2 class="page-header">Promise 封装 AJAX操作</h2>
    <button class="btn btn-primary" id="btn">点击发送 AJAX</button>
  </div>
  <script>
    //接口地址 https://api.apiopen.top/getJoke
    //获取元素对象
    const btn = document.querySelector('#btn');

    btn.addEventListener('click', function () {
      //创建Promise
      const p = new Promise((resolve, reject) => {

        //1.创建对象
        const xhr = new XMLHttpRequest();
        //2.初始化
        xhr.open('GET', 'https://api.apiopen.top/getJoke')
        //3.发送
        xhr.send();
        //4.处理响应结果
        xhr.onreadystatechange = function () {
          if (xhr.readyState === 4) {
            //判断响应状态码 2xx
            if (xhr.status >= 200 && xhr.status < 300) {
              //控制台输出响应体
              resolve(xhr.response)
            } else {
              //控制台输出响应状态码
              reject(xhr.status)
            }
          }
        }
      })
      //调用then方法
      p.then(value=>{
        console.log(value)
      },reason=>{
        console.warn(reason)
      })
    })
  </script>
</body>

</html>